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Farming Under Water

Over the last year I’ve had the opportunity to visit a mountain farm raising trout in concrete runs. I’ve seen tilapia and sturgeon raised indoors in large tanks. I’ve stood on the banks of a catfish pond in the eastern part of the state.   I’ve met watermen and women who catch crabs, shrimp, and various fish in the waters off the coast. I’ve toured Millpoint Aquaculture, the only commercial clam and oyster hatchery in North Carolina, where we rode a boat to check a crop of farm-raised oysters in the Core Sound.

Oyster Hatchery
Millpoint Oyster Hatchery, located on the banks of the Core Sound

The amount of aquaculture, which is defined by the NC Aquaculture Development Act as “the propagation and rearing of aquatic species in controlled or selected environments, including, but not limited to, ocean ranching” in my state quite honestly amazes me. It’s a part of agriculture that may not receive as much recognition as other types of farming, but its effect on the culture and economy in our state can’t be denied.

I could write multiple posts on all the things I’ve learned from these farm tours. Honestly, I’ve struggled with how to condense it into one post. Finally, I decided to focus on oyster farming. The system, licenses, and regulations are more complex than I could ever describe in a single post, but I’ve narrowed it down to three things I learned about oyster farming in NC.

     1.  Oysters can be caught in the wild or farm raised.

Wild oysters are harvested from a boat using tongs – long wooden poles with rakes on the ends. The tongs are used to rake the oysters on the bottom and lift them onboard. In my state, anyone can harvest wild oysters from public waters. If the oysters are going to be sold, a commercial fishing license is required so all oyster farmers have a commercial license.

Farm-raised oysters are managed by watermen. There are different systems farmers can use to raise oysters, but they all have the same goal: to raise a healthy oyster. Most farm-raised oysters are destined for the half shell market.  

Oyster Baskets in the Sound
Farm raised oysters in floating baskets on leased water in the Sound

I was surprised to learn the state monitors the area after heavy rainfall due to potential runoff into oyster-growing areas. If an area has received too much rain, waters are closed for harvest. Water quality is extremely important since the oyster not only grows in the water but filters water for food. One adult oyster can filter 30 to 50 gallons of water each day. We were the only boat on the water in Nelson Bay because waters were closed to harvest, but several miles away in Morehead City, they were open.  

I’ve always been told you only eat oysters in months that end in “r,” but it turns out that’s an old wives’ tale. You can eat them year-round, but the quality is lower in the summer months because the oyster is putting its energy into spawning (reproducing), not meat production. This is especially true for wild-caught oysters. Most farm-raised oysters are triploids (some wild caught are too) and are sterile, so all their energy goes to meat production.

        2.  Farmers raising shellfish, including oysters and clams, pay farm rent.  

North Carolina has been leasing public waters for private use to grow shellfish on the bottom since 1858. The first water column lease was signed in 1991. Under this lease, the crop (in this case, oysters) can’t touch the bottom, even though the fisherman is required to lease that, too. 

Now called the Shellfish Lease and Franchise Program, it is administered by the North Carolina Division of Marine Fisheries. Leases are only given for areas where wild shellfish are not growing. Once approved, leases are good for 10 years before they come up for renewal.

In addition to paying rent, fishermen must meet production requirements.  For example, in 2016 an oyster farmer was required to harvest 40 bushels per acre from the water column or plant 100 bushels of seed per acre.

There are no new leases available in the Core Sound, where we visited. A fisherman can take over an existing lease, which only becomes available when a fisherman doesn’t reapply. 

      3.  It can take up to two years for oysters to reach harvest size.

I guess because oysters are small, I thought they would reach harvest size pretty quickly. I was wrong. From microscopic larvae to mature size, the waterman has invested from one to two years in the crop.  

Most oyster farmers buy seed, the baby oysters, from a commercial hatchery. This is a complex operation. Oysters are broadcast spawners, releasing eggs and sperm and hoping they meet in the water. Water is drained through a sieve that catches the eggs. Under a microscope, eggs are checked to see if they are fertilized.  

Eggs are then moved to large stock tanks, where they are so small the only way to see them is by shining a flashlight through the side. Even then, if you didn’t know what you were looking at, it would be easy to miss the microscopic larvae. 

Microscopic Oyster Larvae
Even with a light, it's hard to see microscopic larvae floating in the stock tank.

The larvae feed on algae, which is grown at the hatchery. As you can see from the photo, it looks like a science lab, not a farm. Each of the tubes holds a different type of algae to meet the needs of immature oysters.

Oyster Hatchery Lab

As they grow, the spat, or baby oysters, are moved outside to shallow tanks filled with seawater. Read more about oyster hatchery techniques in Publication 4302 from the Southern Regional Aquaculture Center.

Raceways for Oyster Production
Spat stay in outdoor raceways until they are large enough for open waters.

When they are 4 mm in size, spat are moved to open water in floating baskets or bags. There, they dine on algae filtered from the water. The flavor of a harvested oyster will vary depending on the type of algae they eat and the water’s salinity.

Watermen check the baskets weekly, turning them so the oysters will be perfectly round. They also clear away any algae that has built up, which would prevent water from filtering though the bag’s holes. As they grow, oysters are moved to bags with larger openings. 

Once they reach 3 to 4 inches in size, oysters are ready to harvest and land on someone’s plate. 

Oyster ready for harvest

 

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